Local newspaper the Waikato Times reported the $NZ3 million, 50-tonne machine is 3.5km from the surface, buried under hundreds of tonnes of coal, and will remain there for up to two weeks.

The shaft collapse occurred as the shuttle car attached to the machine was undergoing repairs from an electrical fault as the result of another minor roof fall.

Mine owner Solid Energy told the Waikato Times no workers were endangered during either collapse and that production would continue but would be "scaled back" while the machine was extracted.

The mine produces about 400,000 tonnes of coal annually, the majority supplied to the Glenbrook power plant.

About 120 employees are hired at the mine.